1. Field of the Invention
This invention relates generally to the field of plastic molding and specifically to shuttle and lock features of a molding apparatus.
2. Description of the Related Art
Plastic parts are commonly molded in an apparatus having a pair of separable mold halves. Generally, one mold half is stationary and the other is movable. The mold halves are closed and molten resin is injected into a cavity defined by the mold. In some cases, a gas is blown into the mold to create a hollow body of the resin. After cooling, the mold halves are separated and the molded part is removed. The operation is then repeated for subsequent parts.
To increase the rate at which parts can be molded, U.S. Pat. No. 4,810,181 to Ozawa, incorporated herein by reference, shows a molding apparatus that alternately shuttles two molds from an injection/unloading station to respective cooling stations. Still, it would be desirable to have a mold shuttling apparatus that allows one mold to cool and be unloaded while the other is filled and blown.
During molding, it is necessary to provide a locking force to maintain the molds in the closed position to withstand the heat and pressure of the molding and blowing. Such a locking force can be provided as a part of the mold closing mechanism, that is, the mold closing mechanism can provide enough force to maintain the mold in the closed position. Alternatively, a separate locking mechanism can be provided to lock the mold in the closed position after it has been closed by a closing mechanism. Examples of different closing and/or locking mechanisms are shown in U.S. Pat. Nos. 3,262,158; 3,327,353; 4,005,964; 4,273,524; 4,432,720; 4,579,519; 4,588,364; 4,594,067; 4,608,005; 4,611,981; 4,626,190; 4,698,012; 4,768,946; 4,810,181; 4,959,191; 5,044,927; and 5,306,325, all incorporated herein by reference. It would be desirable to provide an improved separate locking mechanism that positively secures the molds in the closed position with a minimum input of force.